<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            display: flex;
            width: 1200px;
            margin: auto;
        }

        .content {
            height: 300px;
            flex: 1;
            border: 1px solid #000;
        }
    </style>
</head>

<body>

    <div class="box">
        <ul>
            <li>
                <a href="#first">first</a>
            </li>
            <li>
                <a href="#second">second</a>
            </li>
            <li>
                <a href="#third">third</a>
            </li>
        </ul>
        <div class="content">
            <!-- 显示对应的内容 -->

            <!-- <div>first</div> -->

        </div>
    </div>

    <script src="./index.js" type="module"></script>

</body>

</html>